Facebook Connect

Facebook Connect (although I now believe it's dropped that name in favour of 'feature of the social graph') is the feature that lets you use Facebook and log onto 3rd party websites with your Fb username and password.

Fair enough. I like the social graph feature, as daunting as it may seem I find that when you sign up to a new site it's handy when you don't have to fill in all of your details every time. Kinda like when a site accepts PayPal. On that note you probably don't want to hear that Facebook is starting its own currency!

Google Connect is fine as an add-on to your site's registration process, but definitely shouldn't be the only registration option.

For example, I work on a niche social networking website, and we're going to at some point integrate Facebook Connect so visitors can register with their details in their Facebook account instead of filling in a registration form manually.